Electronic devices include traditional computing devices such as desktop computers, notebook computers, smartphones, wearable devices like a smartwatch, internet servers, and so forth. However, electronic devices also include other types of computing devices such as personal voice assistants, programmable thermostats, automotive electronics, robotics, intelligent devices embedded in other machines like refrigerators and industrial tools, Internet-of-Things (IoT) devices, and the like. These various electronic devices provide information, entertainment, social interaction, security, safety, productivity, transportation, and other services to human users. Thus, electronic devices play crucial roles in many aspects of modern society.
Many of the services provided by electronic devices in today's interconnected world depend at least partly on electronic communications. Electronic communications can include those exchanged between or among distributed electronic devices using wireless or wired signals that are transmitted over one or more networks, such as the Internet or a cellular network. Electronic communications can also include those exchanged between or among different printed circuit boards, modules, chips, or even cores of a given integrated circuit that are located within a single electronic device. Regardless, electronic communications are usually accomplished by generating or propagating signals. Such electronic communications are typically performed using at least one signal that is designed to have a specified characteristic, such as a particular frequency. Generally, communication signals are more likely to be correctly transmitted and received, as well as properly interpreted, if the specified signal characteristic is accurately and reliably produced.
With regard to a frequency signal characteristic, a frequency synthesizer can be used to create, or synthesize, a desired frequency. Thus, electronic devices employ frequency synthesizers to synthesize signals having desired frequencies. Typically, a frequency synthesizer includes a frequency generator. Examples of frequency generators include a phase locked loop (PLL), a frequency locked loop (FLL), and so forth. In operation, a frequency generator receives a reference signal having a reference frequency and applies the reference signal to a feedback loop. Using the feedback loop, the circuitry of the frequency generator generates an output signal that oscillates at a desired output frequency in a stable and accurate manner based on the reference frequency. The frequency generator can derive the output frequency of the output signal based on the reference signal, such as by driving the output frequency to have some multiple of the reference frequency of the reference signal.
A frequency synthesizer therefore outputs an oscillating signal having some desired frequency. The electronic device can use the synthesized frequency of the oscillating output signal in one or more stages of a communication scenario. Example stages for communicating an electromagnetic signal include generating, transmitting, receiving, and interpreting a communication signal. In an example signal-generation stage, a frequency generated by a frequency synthesizer can be used to modulate a communication signal. Here, the modulation entails encoding or adding information—such as a text and an associated photograph—to the communication signal. In an example signal-transmission stage, a frequency generated by a frequency synthesizer can be employed to upconvert a frequency of a modulated communication signal using a mixer. With an up-conversion operation, the mixer increases the frequency of the communication signal, such as to enable the communication signal to be transmitted wirelessly as a radio frequency (RF) signal between a smartphone and a cellular base station.
A frequency synthesizer can also be used with the stages of a reception side of a typical communication scenario. For instance, a frequency synthesizer can be used to down-convert a frequency of a received communication signal. After down-conversion, a frequency synthesizer can be used to demodulate the down-converted communication signal to interpret the signal and thereby recover encoded information, such as the text message along with the associated photograph. Additionally, a frequency synthesizer can be used to produce a clock signal that controls a rate of operation of clock-synchronized circuitry of an integrated circuit. Examples of such integrated circuits include a system-on-chip (SoC) that processes a communication signal and a graphics chip that processes video data that is being displayed to a user.
Thus, frequency synthesizers can be employed in multiple stages of a communication scenario to support electronic communications with electronic devices and in synchronous circuitry to support coordinated interoperations among different components of electronic devices. Consequently, electrical engineers and other designers of electronic devices strive to improve the functionality and usability of frequency synthesizers to facilitate electronic communications and high-speed synchronous operations by electronic devices.